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  1. #1
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    Oct 2006

    RST M-29 service / fluid overhaul

    Had mentioned in this thread that I'd be doing a fluid exchange and overhaul, had some interest so, to those who are interested - read below .

    For those that wanted to know Ė hereís a brief pictorial of the M-29 innards taken during my fork service yesterday. My M-29 is a 100mm model, acquired in Aug 07, with remote lockout. The fork had 1200.77 miles on it when I did the service. At an average of 8.3 mph on my Cateye computer, that puts hours at roughly 144.6 hours of operation. The RST manual lists service periods:

    Normal conditions
    - short sporadic rides = every 6 months
    - long frequent rides = every 4 months

    Severe conditions
    - short sporadic rides = every 4 months
    - long frequent rides = every 3 months

    They donít define normal vs. severe conditions and what long vs. short is. In my case, it took me 5 months to hit 1000 miles with rides from 7 miles to 42 miles in length. Terrain is typical rooty southeast stuff, lots of suspension cycling. I would hazard a guess that I fit the long frequent rides under severe conditions. Just a guess. That being said Ė every 3 months is probably adviseable (once to start the season, once in the middle of the season if you ride 6 mos a year) with the OEM fluid, however, the Silkolene stuff I used is very good based on my research and once every 1000 miles should be good enough with that stuff.

    My overall assessment of the fork and longevity Ė itís got a good service life potential. There was good, some bad and some frustration. This was my first shock overhaul so that played a factor. My biggest gripe in the whole thing is the directions really suck. They were translated into English and some things just did not carry over. Pics were small and obscure, and the instructions go top to bottom, not left to right (i.e. not intuitive to read). Furthermore Ė they mix in 3-4 types of forks so some instructions applied, some did not. I spent about an hour pre-reading, marking what I had to do, what I did not and correcting instructions based on what made sense. Iíve built up 3 bikes now so I figured I needed to add fork service to my repertoire. I can see why people pay PUSH Ė it wasnít hard but sometimes, money is worth the time.

    Positive aspects
    - lowers/finish very durable, barely any paint wear underneath the brake cable
    - easy enough to do at home if you have two left hands and patience.
    - tight tolerances on the air chamber, good indicator on longevity
    - all the screws/fittings were true to size, no chance of rounding a corner on the rebound/air chamber bolts
    - new fluid make the fork feel very smooth again, though I get some ramping in the last inch I never noticed before

    Negative aspects
    - the remote lockout is the most frustrating part to deal with on the whole fork Ė literally. Thatís a shame b/c the remote lockout is my favorite feature, so easy to just flick the thumb and stand up to attack a hill.
    - the black plastic cap on the bottom of the air chamber side stanchion was over torqued Ė could not get it off (fortunately, the tolerances are tight and it was pretty well lubed at the factory so no need to pull out the bottom seal. 10cc fresh Silkonene in the chamber and it was good)
    - the instructions SUCK
    - my rebound knob was cracked Ė would be better if this were aluminum

    other observations
    - the instructions leave a lot to be desired. I documented just as a backup for reassembly.
    - I donít know what weight fluid was originally in the fork, the service desk told me 15wt. What came out was no longer 15wt, it was at best, 5wt, though I think it was even lower than that. I use 5W-30 in one of my cars and it was not that thick. Pretty thin, dirty and foamy (pic below). It was clear it had lost itís viscosity. I suppose you could add some anti-foaming agent to the fresh fluid, like the stuff used in auto rear ends for limited slip differentials, or just use high quality fork fluid. The research I did after reading Mikeseeís post on Silkolene led me to that choice. The Silkolene fluid is made by Fuchs. Rave reviews on the motorcycle side with this stuff. I can tell you the fork action is more Ďcompetentí now. I do feel a bit of ramping towards the last inch of travel, something I did not notice before. I would recommend using only 140cc of fluid instead of the 145cc listed in the instructions. I may pop open that leg and dip a paper towel in to soak up a bit of excess fluid, after a few rides, Iím not getting full travel. I managed to get 92mm of the 100mm yesterday on the back patio push down test. It would have to be a significantly noticeable lack of travel though, see first comment under the negative aspects listed above. Iíd rather wrestle a pack of wild weasels while covered in peanut butter than mess with the remote lockout just to remove 5cc of fluid.

    Would I buy another M-29? Without hesitation. That being said, Iím drooling over the new 09 Reba with the maxle light Ė will be an awesome match to my Sultan. The RST will move on to a 29er frame Iíll build up for my wife as my youngest girl moves from her 24Ē bike to a full size bike. Itís worth keeping around.

    On to the pics

    Tools necessary ( most of them anyway) , easy stuff, nothing abnormal other than some c-clip style pliers

    C-clip pliers needed to hold the remote lockout top still while unscrewing it.
    Happiness depends more on the inward disposition of mind than on outward circumstances. Benjamin Franklin

  2. #2
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    Oct 2006
    Remote lockout spring – the part that wanted to make me say bad four-letter words

    Top of the rebound leg (right leg). The holes are for the normal ball/detent rebound lever.

    Underside of the remote lockout, plenty of lube from the factory

    Beefy dropouts, this is the air chamber (left leg) side, one bolt holds down the inner piston, it’s got a thick rubber bumper at the base that’ll stick to the grease in the bottom when you pull it apart so you’ll have to shake that piece out (one of the gems that was not in the instructions)

    Cracked rebound knob – the long piece is inside the leg, found the crack after removing it

    Plenty of grease and thick rubber O-rings used on each leg cap, this is the air chamber side

    The rebound mechanism is reverse threaded. They don’t mention that in the instructions, however, Fixgeardan did so I was tracking on this. Instructions say turn ‘clockwise, which is right but counterintuitive to saying it’s reverse threaded.
    Happiness depends more on the inward disposition of mind than on outward circumstances. Benjamin Franklin

  3. #3
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    Oct 2006
    A look down the outers – grease in the leg is what I pumped in through the grease ports – don’t know how much is original. I lubed the legs twice in the 1200 miles. Probably a bit too much – I cleaned most of it out.

    Bottom out bumper on the bottom of the reverse threaded rebound leg (keep in mind, that nut has to be screwed back on so the threads can be threaded into the lowers, instructions didn’t mention that either)

    This is the bottom of the air chamber leg, the grooves were made from my c-clip pliers which I was supposed to use to unscrew the cap and pull out the bottom seal. It was over torqued so it didn’t come off. I cleaned up the grooves with some sand paper and left it as is.

    Rebound assembly, right leg

    Foamy old fluid

    Dirty old fluid

    Bottom portion of the upper air chamber seal, with OEM grease and burly rubber O-rings – tight seal. I had to release air from the air valve to push this down the leg it was that good at sealing.

    Ok – it’s not the sexy blue PUSH o-ring but this number is cooler than the zip tie travel indicator. Came from a faucet repair kit I found at Home Depot.

    I had 6mm of thread that stripped from the top post mount last month so I helicoiled both PMs. The threads were 16mm deep which is a good thing. I was able to install two complete helicoils, with blue loctite. Pics below of the helicoil process. Peace of mind knowing there’s a more solid thread surface now, with longevity for multiple removals. 80 in/lbs on the Avid CPS and life’s good.

    That’s it for the pics – if anyone needs the instructions, shoot me a PM with your email address and I’ll email the .pdf files.
    Happiness depends more on the inward disposition of mind than on outward circumstances. Benjamin Franklin

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